1. Field of the Invention
The present invention relates to a communication system and a communication apparatus, and more particularly to a communication system and a communication apparatus for adjusting or arbitrating the communication time periods of a working communication path and a protection communication path.
2. Description of the Related Art
In general, with increase in a demand for a broad band, the introduction of a large-capacity access line employing an optical fiber has advanced as a user-oriented access line, instead of communication technology which is based on a telephone line such as digital subscriber line (DSL). At present, a passive optical network (PON) system in which the optical fiber can be shared by a plurality of subscribers is often utilized as the optical access line from the viewpoints of a line laying cost and a maintenance management cost. The PON system which can manage connection situations and bandwidth utilization situations concentrically on the side of a station building, by multiplexing traffics that flow between the plurality of users and the station building, is one of major techniques in a subscriber line service in the future.
In “ITU-T” (International Telecommunication Union Telecommunication Standard Sector) which is one of international standardization organizations, a “G-PON” (Gigabit capable PON) system has been stipulated (Non-patent Documents 1 to 3). In 2006, many vendors started providing GPON products into markets, and common carriers in individual countries simultaneously started optical access services based on the adoption of the GPON. Besides, some common carriers are providing optical access services by employing “GE-PON” (Gigabit “Ethernet” (registered trademark) PON) (Non-patent Document 4) which has been stipulated by “IEEE” (Institute of Electrical and Electronics Engineers, Inc.) being another international standardization organization.
In transmission networks, shifts to packet communication techniques such as “Ethernet” (registered trademark) and “MPLS” (Multi Protocol Label Switching) have been studied instead of an existing “SONET” (Synchronous Optical NETwork)/“SDH” (Synchronous Digital Hierarchy) technique, and an existing “ATM.” (Asynchronous Transfer Mode) technique. In the packet communication network, a packet format consisting of a header and a payload is configured, and a relaying device processes each packet on the basis of a destination ID and a transmission source ID which are contained in the header part, relevant path control information items, etc. A communication aspect on this occasion is not a scheme in which signals are transmitted and received by employing statically set paths as in the existing synchronous network or ATM network, but a communication scheme in which respective packets undergo different communication paths. When note is taken of part of the path, a series of packets having the same header information do not occupy the path, but a plurality of packets having header information items different from one another exist on the path at the same time.
At present, the communication network is becoming an indispensable existence as a social infrastructure. The lowering of the prices of communication services has been required together with the spread of the communication network. In this flow, it is thought substantially obvious to lead to the idea that the infrastructure is configured in a form in which the optical access network and the packet communication network is combined. On the other hand, a high stability is required for providing the infrastructure. However, the development of a maintenance management function for enhancing a stability forms a factor for a cost expansion.
As one method for coping with the contradictory requirements of realizing the lowering of the price and ensuring the high stability, there has been studied a method in which, for the pseudo maintenance management of paths in the packet communication, “ULAN” (Virtual Local Area Network) in “Ethernet” (registered trademark) and “LSP” (Label Switch Path) in the MPLS are set, whereupon their continuity is managed. The idea that the path is set on the packet communication network in pseudo fashion and that the path is maintenance-managed, is a useful idea in the coexistence of the packet communication network with the existing network and the shift thereof from the existing network. As a typical example, an Ether “OAM” (Operation, Administration and Maintenance) technique is mentioned (Non-patent Document 5). Further, a protection switching technique based on the Ether OAM (Non-patent Document 6) has been standardized.    [Non-Patent Document 1] ITU-T Recommendation G.984.1, “Gigabit-capable Passive Optical Networks (GPON): General characteristics”    [Non-Patent Document 2] ITU-T Recommendation G.984.2, “Gigabit-capable Passive Optical Networks (GPON): Physical Media Dependent (PMD) layer specification”    [Non-Patent Document 3] ITU-T Recommendation G.984.3, “Gigabit-capable Passive Optical Networks (GPON): Transmission convergence layer specification”    [Non-Patent Document 4] IEEE 802.3-2005, “IEEE Standard for Information technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific requirements Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications”    [Non-Patent Document 5] ITU-T Recommendation Y.1731, “OAM functions and mechanisms for Ethernet (registered trademark) based networks”    [Non-Patent Document 6] ITU-T Recommendation G.8031/Y.1342, “Ethernet (registered trademark) Protection Switching”